Both the axial density and temperature profiles of ground-state nitrogen atoms have been measured in a microwave discharge and its afterglow in the presence of the so-called short-lived afterglow by means of two-photon absorption laser-induced fluorescence (TALIF). The temperature is obtained from the Doppler broadening of the spectral profile, after deconvolution with the laser profile. The N atom temperature decreases from about 1400 K in the end of the discharge zone to about 300 K in the downstream part of the afterglow. The sharp temperature decrease immediately behind the discharge zone can reasonably be explained by heat transfer to the flow tube wall. The absolute N atom density is obtained by calibrating the fluorescence yield with a TALIF signal from krypton atoms. The N density increases from 1.5×10²¹ m^-3 in the discharge zone to about 3.5×10²¹ m^-3 in the late afterglow. However, the N atom flux is conserved along the flow tube, indicating negligible consumption or production of N atoms in the short-lived afterglow.

The first absolute density measurement of N₂(A ³Σ⁺_u;v = 0) metastable molecules in the short-lived nitrogen afterglow of a 440 Pa microwave discharge is achieved by using a intracavity laser absorption spectroscopy technique. The results obtained show that this technique is very well suited for the diagnostics of N₂(A ³Σ⁺_u) in the nitrogen afterglow. This is a first important experimental step with the aim of probing regions where the densities are expected to be the most significant. The densities measured in the discharge zone and in the short-lived afterglow maximum emission zone are about 5×10¹⁷ and 6×10¹⁶ molecule m^-3, respectively. The gas temperature is also deduced both from the Doppler profile of the spectrally resolved rotational lines and from the rotational distribution in the N₂(A ³Σ⁺_u;v = 0) state. These temperatures are about 1000 K in the discharge zone and 530 K in the short-lived afterglow maximum emission zone, respectively. The relatively high density of metastable molecules in the short-lived afterglow maximum emission zone reveals the important role played by these species in the short-lived nitrogen afterglow and can give a new insight into the mechanisms involved in the so-called nitrogen short-lived afterglow emission. We also conclude that this high density of N₂(A ³Σ⁺_u) in the short-lived afterglow results from an equilibrium between some local production mechanisms and destruction by reaction with N atoms.

Properties both of the discharge and of the post-discharge region are studied through the so-called short-lived afterglow generated at 340 Pa by two similar coaxial cavities resonating at 433 and 2450 MHz. Simultaneous Raman Stokes scattering and optical emission spectroscopies are performed. The gas temperature profiles of the various regions are built up through exploitation of and rotationally resolved spectra and by application of an original method involving the densities estimated from the Raman spectra. In the post-discharge region, the latter give the Treanor temperature which is assimilated to the vibrational temperature of in the discharge. The vibrational distribution function of in the short-lived afterglow is compared with the Treanor-Gordiets-like model and found to exhibit a larger excitation at 433 MHz. In this region, the model predicts a marked maximum of the average vibrational energy per molecule at a position where emissions' intensities are also the highest. The correlation of and densities shows that the 2450 MHz frequency has a slightly larger density in our case than it has for the other case. These results are discussed through the comparison of these two plasma sources in terms of production of molecular metastable electronic states and Penning ionization.

In the present work, the dielectric properties of recycled liquid crystals (LCs) (non-purified, purified, and doped with diamond nanoparticles at 0.05, 0.1, and 0.2 wt%) were investigated. The studied LC mixtures were obtained from industrial recycling of end-of-life LC displays presenting mainly nematic phases. Dielectric measurements were carried out at room temperature on a frequency range from 0.1 to 10⁶ Hz using an impedance analyzer. The amplitude of the oscillating voltage was fixed at 1 V using cells with homogeneous and homeotropic alignments. Results show that the dielectric anisotropy of all purified samples presents positive values and decreases after the addition of diamond nanoparticles to the LC mixtures. DC conductivity values were obtained by applying the universal law of dielectric response proposed by Jonscher. In addition, conductivity of the doped LC mixtures is lower than that of the undoped and non-purified LC.